1. Field of the Invention
The present invention relates to a novel wastewater treating system for removing carbon, nitrogen and phosphorous and the method thereof. More particularly, to apply methanogenic bacteria in the wastewater treating system, which is able to lower the production volume of the residual sludge and decrease the problem of power consuming.
2. Description of Related Art
The design of early wastewater treatment system usually comprises with the purpose of decreasing the organic pollution, which prevents the pollutants flow into water and consumes the oxygen of the water due to the organism decomposed by the microorganism and causes the decreasing of the dissolved oxygen in the water then affects the living of the aquatic creature. However, the domestic wastewater includes not only the organisms but it also includes abundant nitrogen, phosphorous, theses compounds are the essential nutrients for the growth of various algae. In the proper temperature and enough sunshine, the abundant nitrogen and phosphorous will make the aquatic algae grow, and causes another damage of the water.
The traditional domestic wastewater usually treats with the active sludge process. It is mainly in the purpose of removing the carbon in the wastewater. Generally it is able to remove 5˜15% phosphorous at the primary treatment (mainly combine with the solid objects). It is able to remove about 10˜25% phosphorous with traditional biological treating method and transforms ammonia nitrogen into nitrate nitrogen by the nitrifying microorganisms, however, it is still limited in the removing ability to whole nitrogen and phosphorous nutrients. Currently, there had been a strict discharging standard of nitrogen and phosphorous nutrients in the domestic wastewater. Taiwan had already made the effluent standard of total concentration of nitrogen in 15 mg/L, total concentration of phosphorous in 2 mg/L of excluding the wastewater into the protective area of water source, quality and volume in the public sewers. However, in order to maintain the aquatic ecology balance effectively and prevent the problem of eutrophication on water body on the earth surface. Moreover, according to the popularity of the development of public sewers in our country, it is necessary to control the discharging of nitrogen, phosphorous nutrients.
The domestic wastewater exists in the form of ammonia nitrogen and organic nitrogen, no matter that it is treated in aerobic or anaerobic biological treating method; the organic nitrogen is easy to be metabolized into ammonia nitrogen. The traditional nitrogen removal process is to apply with the microorganism in the aerobic condition. It oxidizes ammonia nitrogen into nitrate-nitrogen, then in the anaerobic condition, to reduce the nitrate-nitrogen into nitrogen gas and spread into the water in order to achieve the purpose of nitrogen removal.
The phosphorous compound is able to remove in the following methods: (1) chemical precipitation: it is obtained the precipitation by adding ions such as, Ca, Fe and Al ions and controlling the pH value, (2) the phosphorous assimilation of microorganism, (3) the microorganism accumulates phosphate, (4) the enhanced chemical precipitation of microorganism control, wherein the microorganism accumulates method of phosphorous removal is widely applied in recent year. Phosphorous is saved in the form of polyphosphate granular objects in the cell, it is considered to be the cell energy and the source of phosphorous. In the wastewater treating system, there is a special microorganism called Phosphate Accumulating Organism (PAO). It releases phosphorous in the anaerobic condition, however it will accumulate large volume of phosphate in the water in the aerobic condition, which is over the physical require. PAO gains the energy by decomposing the polyphosphate salt in the bacteria in the condition of non-dissolved oxygen and non-combining oxygen. It processes absorption of low molecule fatty acid such as acetic acid (from facultative bacteria hydrolysis product or exist in the wastewater already) and synthesizes poly-β-hydroxybutyrate (PHB) to save in the cell. Polyphosphate granular object is decomposed and release phosphorous into the wastewater. In the aerobic condition, PAO is treating oxygen as an electron acceptor and aerobic decomposes the PHB in the bacteria or external carbon for producing the energy. Apply the energy for absorbing the phosphate in the wastewater and then transforming into polyphosphate in the bacteria in order to remove the exceeded sludge for achieving the purpose of removing phosphate in the wastewater.
In order to achieve removing nitrogen and phosphate in the same time in one wastewater treating system, basically, a wastewater treating system has to comprise three different oxidation states, (Anaerobic-Anoxic-Oxide Activated Sludge Process, A2O) (show as in FIG. 1). It is usually used for treating the wastewater includes organic carbon, phosphorous and nitrogen in order to make the wastewater pass through the biological treating process of anaerobic, anoxic and aerobic for achieving the effect of nitrogen removal and phosphorous removal at the same time. The microorganism of A2O treating process is nitrifying bacteria, denitrifying bacteria, PAO and the heterotrophic bacteria of lowering the chemical oxygen demand (COD). In the anaerobic reactor, when denitrifying bacteria and PAO are processing the phosphorous and nitrogen removal, it is necessary to provide organic carbon for metabolism, and the organic compound left from the phosphorous and nitrogen removal process of denitrifying bacteria and PAO decomposes in the aerobic reactor by the heterotrophic bacteria. The aerobic reactor provides a place for nitrifying of ammonia nitrogen and the mineralization of the organic compound; therefore, the traditional A2O treating process is able to produce large volume of residual sludge in the normal operation. If the process is designed or operated improperly, it is easy to cause the shortage of nitrifying bacteria and the failure of nitrogen removal. Zenon company combine the membrane filtering technology and the A2O treating process, it solves the problem of losing nitrifying bacteria. Although, it solves the problem of losing nitrifying bacteria but causes a large volume of sludge and causes large power consuming, therefore, it still cannot overcome the problem of the deficiency in nitrogen removal.
The Taiwan patent application number 92132719 disclosures an organic-pollutant-included wastewater treating system, comprising an anaerobic bioreactor, aerobic bioreactor and a membrane separation reactor; wherein the aerobic bioreactor is disposed rearward of the anaerobic bioreactor, the membrane separation reactor is disposed rearward of the aerobic bioreactor, the system is capable of eliminating organic pollutants in wastewater by using a biological processing method, and separating solid substances from the liquid ones by using a membrane. The organic-pollutant-included wastewater treating system is able to remove the organic pollutants effectively and solve the problem of the scaling and the fouling on the surface of membrane. However, the objects in the wastewater comprise not only organic pollutants but also carbon, nitrogen and phosphorous, therefore, to develop a wastewater treating system which is able to remove carbon, nitrogen and phosphorous in the same time and improve the problem of causing a large volume of sludge and power consuming of the traditional wastewater system (for example, A2O), it is truly a fine subject for research.
Therefore, it is desirable to provide an improved speech recognition method to mitigate and/or obviate the aforementioned problems.